class ActiveSupport::MessageEncryptor
MessageEncryptor is a simple way to encrypt values which get stored somewhere you don't trust.
The cipher text and initialization vector are base64 encoded and returned to you.
This can be used in situations similar to the MessageVerifier
,
but where you don't want users to be able to determine the value of the
payload.
salt = SecureRandom.random_bytes(64) key = ActiveSupport::KeyGenerator.new('password').generate_key(salt) # => "\x89\xE0\x156\xAC..." crypt = ActiveSupport::MessageEncryptor.new(key) # => #<ActiveSupport::MessageEncryptor ...> encrypted_data = crypt.encrypt_and_sign('my secret data') # => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..." crypt.decrypt_and_verify(encrypted_data) # => "my secret data"
Constants
- DEFAULT_CIPHER
- OpenSSLCipherError
Public Class Methods
Given a cipher, returns the key length of the cipher to help generate the key of desired size
# File lib/active_support/message_encryptor.rb, line 70 def self.key_len(cipher = DEFAULT_CIPHER) OpenSSL::Cipher.new(cipher).key_len end
Initialize a new MessageEncryptor.
secret
must be at least as long as the cipher key size. For
the default 'aes-256-cbc' cipher, this is 256 bits. If you are
using a user-entered secret, you can generate a suitable key by using
ActiveSupport::KeyGenerator
or a similar key derivation
function.
Options:
-
:cipher
- Cipher to use. Can be any cipher returned byOpenSSL::Cipher.ciphers
. Default is 'aes-256-cbc'. -
:digest
- String of digest to use for signing. Default isSHA1
. -
:serializer
- Object serializer to use. Default isMarshal
.
# File lib/active_support/message_encryptor.rb, line 47 def initialize(secret, *signature_key_or_options) options = signature_key_or_options.extract_options! sign_secret = signature_key_or_options.first @secret = secret @sign_secret = sign_secret @cipher = options[:cipher] || 'aes-256-cbc' @verifier = MessageVerifier.new(@sign_secret || @secret, digest: options[:digest] || 'SHA1', serializer: NullSerializer) @serializer = options[:serializer] || Marshal end
Public Instance Methods
Decrypt and verify a message. We need to verify the message in order to avoid padding attacks. Reference: www.limited-entropy.com/padding-oracle-attacks.
# File lib/active_support/message_encryptor.rb, line 65 def decrypt_and_verify(value) _decrypt(verifier.verify(value)) end
Encrypt and sign a message. We need to sign the message in order to avoid padding attacks. Reference: www.limited-entropy.com/padding-oracle-attacks.
# File lib/active_support/message_encryptor.rb, line 59 def encrypt_and_sign(value) verifier.generate(_encrypt(value)) end
Private Instance Methods
# File lib/active_support/message_encryptor.rb, line 90 def _decrypt(encrypted_message) cipher = new_cipher encrypted_data, iv = encrypted_message.split("--".freeze).map {|v| ::Base64.strict_decode64(v)} cipher.decrypt cipher.key = @secret cipher.iv = iv decrypted_data = cipher.update(encrypted_data) decrypted_data << cipher.final @serializer.load(decrypted_data) rescue OpenSSLCipherError, TypeError, ArgumentError raise InvalidMessage end
# File lib/active_support/message_encryptor.rb, line 76 def _encrypt(value) cipher = new_cipher cipher.encrypt cipher.key = @secret # Rely on OpenSSL for the initialization vector iv = cipher.random_iv encrypted_data = cipher.update(@serializer.dump(value)) encrypted_data << cipher.final "#{::Base64.strict_encode64 encrypted_data}--#{::Base64.strict_encode64 iv}" end
# File lib/active_support/message_encryptor.rb, line 106 def new_cipher OpenSSL::Cipher.new(@cipher) end
# File lib/active_support/message_encryptor.rb, line 110 def verifier @verifier end